The earliest proven ancestor
of the house of Hohenzollern seems to have been one Friedrich I Graf von
Zollern who m.Udilhild, probably dau of Egino Gf von Urach von Urach and had
issue:

1a) Friedrich II (d.after
1145; m.NN

1b) Friedrich
I (III), 1192 Burggraf von Nürnberg, Gf von Zollern (d.after 1 Oct 1200); m.Sophie
von Raabs, widow and heiress of Konrad, the last of the old Burggraves of
Nürnberg; they left two sons, ancestors of the two branches of the family still
extant; it seems uncertain which was the elder son, but genealogies usually
state that Friedrich was the elder